View Full Version : Possible cause of MAF malfunction
Well, we all know 20VT MAFs are quite touchy, but i had a chat with a mechanic friend of mine yesterday when we fixed a problematic ibiza 20VT whose MAF has been shagged just after (ca. 10 miles) ECU remapping. He told me that he fixed several VW TDIs with the same problem (MAF getting knackered right after tuning - engine lacking of power and spewing black smoke).
His opinion is that the MAFs are used to a specific level of maximum airflow and when a higher flow is forced through them they simply fail. When a car is chipped right at the beginning there's no problem...
No idea if it makes any sense -- quite unbelievable, but i've seen this with a 20VT this week (stock paper filter & airbox) with me own eyes.
ibizacupra
29-05-2002, 08:24
Originally posted by Sim
Well, we all know 20VT MAFs are quite touchy, but i had a chat with a mechanic friend of mine yesterday when we fixed a problematic ibiza 20VT whose MAF has been shagged just after (ca. 10 miles) ECU remapping. He told me that he fixed several VW TDIs with the same problem (MAF getting knackered right after tuning - engine lacking of power and spewing black smoke).
His opinion is that the MAFs are used to a specific level of maximum airflow and when a higher flow is forced through them they simply fail. When a car is chipped right at the beginning there's no problem...
No idea if it makes any sense -- quite unbelievable, but i've seen this with a 20VT this week (stock paper filter & airbox) with me own eyes.
I would be interested in the failure mode of the MAF itself. Understanding this would then confirm what might be the cause.
I have heard that they are generally "fragile" and also that wire breakages are one of the causes of failure. Airflow into the inlet would have no effect on the wires into the multiplug.
regards
Bill
firstborn
29-05-2002, 13:13
As an aside, how much does it cost to replace the MAF if faulty. I seem to recall someone saying you can get a VW part fairly cheaply from the states.
Also what are the signs of a faulty/damaged MAF - can you test one?
I want to at least replace the filter panel with a K&N jobby - but if I risk causing £100's of damage I porbably wouldn't chance it.
I have heard that they are generally "fragile" and also that wire breakages are one of the causes of failure. Airflow into the inlet would have no effect on the wires into the multiplug.
No wires in '98 (or so) and later models. It's replaced with some kind of film (www.tdiclub.com).
ibizacupra
30-05-2002, 08:13
Originally posted by Danny
No wires in '98 (or so) and later models. It's replaced with some kind of film (www.tdiclub.com).
The wires to the connector I meant, as opposed hot wire air mass meter. They are hot film MAF's these days.
There is minimal cable strain relief on the connectors and the plastic conduit trunking the wires feed through is pretty heavy compared to the lightweight wires into the connector. Given everything is moving around and vibrating, this will be fatiguing the wires, and they WILL brake. It is just a question of when.
We make virbating instruments, and oscillations, undetectable to the eye always break wires. Stick a strobe on them during running and movements can be seen at certain resonate frequencies.
Do you know if the Film is the failure mode?
Bill
>>Also what are the signs of a faulty/damaged MAF - can you test one?
1)runs rich, sucks more fuel
2)boost wont rise over 0.5bar -safe mode-
3)you TCS might not work
I know, I have broke my MAF and changed it.
holloway
30-05-2002, 09:13
My car cuts out at high revs in third fourth and fith! Seat are changing my MAF cause they siad it could be that? its fine around town just when you open it up in the motorway with load and it struggles through the revs!
:( :confused: :confused: :confused: :confused:
Originally posted by ibizacupra
The wires to the connector I meant, as opposed hot wire air mass meter.
Ok, that's clear.
Do you know if the Film is the failure mode
I'm not sure... I believe the ECU can detect a faulty MAF, but it might be due to the huge resistance of the broken cable... (If I understood your question correctly)
Originally posted by ibizacupra
I would be interested in the failure mode of the MAF itself. Understanding this would then confirm what might be the cause.
I have heard that they are generally "fragile" and also that wire breakages are one of the causes of failure. Airflow into the inlet would have no effect on the wires into the multiplug.
regards
Bill
1552 did not show any MAF related problems, exept for mixture being too lean. When MAF got disconnected, signal too weak achieved. The faulty MAF was however giving fairly correct values until ~3.5-4k RPM, so it was actually working(!), but wrongly. I don't think the wires broke or something.
Originally posted by firstborn
As an aside, how much does it cost to replace the MAF if faulty.
Genuine VAG MAF for the 1.8T is very expensive (~450EUR/~290GBP incl.VAT). I would not try any aftermarket parts in my engine management.
Can it not be sourced from a Bosch dealer quoing the part number cast into the MAF body?
holloway
09-06-2002, 21:06
Changing my MAF sensor sorted my car right out!!!!